EIS and local resolved current density distribution analysis on effects of MPL on PEMFC performance at varied humidification

The performance of two MEA samples with different kinds of gas diffusion layer (with and without micro-porous layer) were investigated at different humidification conditions. Throughout the experiment, segmented cell technique was applied to record the current density distribution. EIS results were recorded combined with the equivalent circuit method to study the internal electrochemical mechanism on performance evolution. The performance of the MEA sample with the micro-porous layer furnished gas diffusion layer improved significantly at both low and high humidification condition. At low load and low humidification condition, the micro-porous layer could retain the product water increasing the hydration level of the membrane and the ionomer in catalyst layers, which greatly reduce the ohmic and activation resistance. Apart from that, the reactant transport resistance is also reduced when product water is retained to hydrate the ionomer, which could be confirmed by the EIS results. At high load and high humidification condition, the micro-porous layer could help curb the flooding in catalyst layer and gas diffusion layer with its excellent water removal capability thus improve the cell performance.